18E.90.030 Seismic Hazard Area Review Procedures

18E.90.030 Seismic Hazard Area Review Procedures.

1. The Pierce County Critical Areas Atlas-Seismic Hazard Area Map provides an indication of where potential seismic hazard areas are located within the County.

2. The Department will complete a review of the Critical Areas Atlas-Seismic Hazard Area Map for any regulated activity to determine whether the site for a proposed regulated activity is located within a seismic hazard area.

3. When the Department's maps indicate that the site for a proposed regulated activity is located within a potential liquefaction or dynamic settlement hazard area, the Department shall require the submittal of a geological assessment as outlined in PCC 18E.90.030 B. below. (See Figure 18E.90-2 in Chapter 18E.120 PCC.)

4. When the Department's maps indicate that the site for a proposed regulated activity is located within a potential fault rupture hazard area, the Department shall require the submittal of a geological assessment as outlined in PCC 18E.90.030 B. below. The requirement to submit a geological assessment may be waived at the Departments discretion when it is determined that the proposed project area for the regulated activity is located outside the potential fault rupture hazard area.

5. When the Department's maps indicate that the site for a proposed regulated activity is or may be located within a potential tsunami or seiche hazard area, the Department shall conduct a review pursuant to the requirements set forth in PCC 18E.70.030.

6. When the Department's maps indicate that the site for a proposed regulated activity is or may be located within a potential earthquake-induced landslide hazard area, the Department shall conduct a review pursuant to the requirements set forth in PCC 18E.80.030.

7. Unless otherwise stated in this Chapter, the critical area protective measure provisions contained in PCC 18E.10.080 shall apply.

B. Geological Assessments. A geological assessment is a site investigation process to evaluate the on-site geology affecting a subject property and define the extent and severity of potential seismic hazards.

1. A geological assessment shall be required when the Department's maps, sources, or field investigation indicate a site contains a potential liquefaction, dynamic settlement, or fault rupture hazard area. Geological assessments shall be submitted to the Department for review and approval together with a seismic hazard area application.

2. A geotechnical professional(s) shall complete a field investigation and geological assessment to determine whether or not the site for a proposed regulated activity is located within a liquefaction or dynamic settlement hazard area. (See Figure 18E.90-2 in Chapter 18E.120 PCC.)

a. The geological assessment shall be submitted in the form of a geotechnical letter when the geotechnical professional(s) finds that no liquefaction or dynamic settlement hazard areas exist within the site. The geotechnical letter shall meet the requirements contained in 18E.90.060 – Appendix A.

b. The geological assessment shall be submitted in the form of a geotechnical evaluation when the geotechnical professional(s) finds that a liquefaction or dynamic settlement hazard area exists on the site but is located outside the proposed project area. The geotechnical verification shall meet the requirements contained in 18E.90.060 – Appendix A.

c. The geological assessment shall be submitted in the form of a geotechnical report when the geotechnical professional(s) finds that liquefaction or dynamic settlement hazard area exists within the proposed project area. The geotechnical report shall meet the requirements contained in 18E.90.060 – Appendix A.

3. A geotechnical professional shall complete a field investigation and geological assessment shall be completed under the responsible charge of an appropriately licensed geotechnical professional and presented in the form of a geotechnical report to determine whether or not the site for a proposed regulated activity is located within a fault rupture hazard area. The geological assessment shall meet the requirements contained in 18E.90.060 – Appendix B. Any structural recommendations proposed to mitigate the fault rupture hazard that are included in the geotechnical report shall be prepared under the responsible charge of an appropriately licensed professional engineer.

4. All geological assessments for seismic hazards submitted under this Chapter shall include at a minimum the following:

a. The dates when the geological assessment was conducted and when the assessment was prepared.

b. The parcel number(s) of the subject property.

c. Site address, if one has been assigned by the County.

d. A brief description of the project (including the proposed land use) and the area to be developed.

e. A map showing the property lines for the site, existing 2-foot contours of the existing site topography, and the location of any existing structures, utilities, wells, stormwater or septic systems, or other developments.

f. A site plan delineating the limits of the proposed development and the location of all areas of the site subject to potential seismic hazards based on the Critical Areas Atlas-Seismic Hazard Areas Map and, if applicable, limits of associated buffers.

g. A description of the surface and subsurface geology, hydrology, soils, and vegetation of the site.

h. A detailed overview of the field investigations, published data and references, data and conclusions from past geological assessments or geotechnical investigations of the site, site-specific measurements, tests, investigations, or studies, as well as the methods of data analysis and calculations that support the determination regarding whether liquefaction and/or dynamic settlement hazards are present on the site.

i. The results, conclusions, and recommendations resulting from the geological assessment of the liquefaction and/or dynamic settlement hazards on the subject property as prepared by a geotechnical professional(s).

5. Geological assessments shall be prepared under the responsible charge of an appropriately licensed geotechnical professional(s) and , signed, sealed, and dated by the appropriate geotechnical professional(s) (as defined in Chapter 18.25 PCC and established in this Chapter) and the format shall be pre-approved by the Department.

6. Geological assessments that do not contain the minimum required information will be returned to the geotechnical professional(s) for revision.

7. The Department shall review the geological assessment and either:

a. Accept the geological assessment and approve the application; or

b. Reject the geological assessment and require revisions or additional information.

8. A geological assessment for a specific site may be valid for a period of up to five years when the proposed land use activity and surrounding site conditions are unchanged. However, if any environmental surface or subsurface conditions associated with the site change during that five-year period, the applicant may be required to submit an amendment to the geological assessment.